The present invention relates to a hydraulic tappet with automatic taking up of the clearance for an endothermic engine which is suited to be mounted between a cam fitted on a camshaft and the end of a valve stem of the above-mentioned endothermic engine.
There are today on the market many and different devices which control the clearance in a continuous and automatic manner by hydraulics.
The present invention relates in particular to a hydraulic tappet of the type comprising two bodies having the shape of a socket, the first of which is partly contained in the second and defines with it an interval chamber suited to be filled with a lubricating liquid, in preference oil, coming from a source under pressure through a duct formed in the walls (lateral and bottom) of the two sockets. The tappet further comprises a ball which cooperates with a conical seat formed in the region of the duct leading in the said chamber; the said ball acts as a member for the interception of the liquid along the duct itself.
Indeed, in order to prevent the exit of the ball from the respective seat, in one modification of the prior art the tappet is provided with a member having an annular form comprising a pair of concentric rings connected by radial arms; said member is in particular snap mounted on a tang protruding axially from a bottom wall of the inner socket toward the said chamber and in a way such that the outer ring occludes the movement of the ball into the chamber. In another arrangement, the ball is retained by the use of a radial pin inserted in a respective radial hole of the said tang. Both of these arrangements, besides being economically expensive, turned out in the long run to be of low reliability. Further, each of them require use of a tang or in any case of a portion protruding from the bottom wall of the inner socket, and this is not always attainable because the chamber in which the liquid flows under pressure must sometimes have a very low height.